LuaExpat 1.5.0

• Warning: this update requires a minimum libexpat version of 2.4.0. Though at the time of writing a minimum version of 2.4.6 is recommended due to CVEs fixed in the intermediate versions.
• Added option allowDTD to the threat protection parser.
• Add configuration for Billion Laughs Attack prevention. This includes adding #include "expat_config.h", since these functions are conditionally included in the exposed API of Expat. This means that LuaExpat will now be compiled using the same options used to compile Expat itself.
• Expose Expat compile time constants (lxp._EXPAT_FEATURES), see Expat documentation.